The invention relates to processes for producing an L-Lysine feed supplement derived from L-Lysine fermentation broth, and more particularly, to producing an L-Lysine feed supplement in which the L-Lysine content is not solely dependent on the initial L-Lysine concentration in the L-Lysine fermentation broth, and still more particularly to a multistep process which can produce a great variety of specifications in order to meet the needs of individual customers.
The term xe2x80x9cdesignated specificationxe2x80x9d is used herein to mean that the invention may be used to provide a product having a unique and custom made specification that is requested by a customer.
Reference is made to parent application Ser. No 09/098,948 filed Jun. 17, 1998 and U.S. Pat. No. 5,990,350 granted on Nov. 23, 1999. The subject matter of both the application and the patent relates to multistep processes for the production of L-Lysine. This subject matter is incorporated herein by this reference thereto.
While this particular specification concentrates on the multistep production of L-Lysine, it should be understood that the invention may be practiced in the production of many amino acids. Hence, the invention is not necessarily limited to the production of L-Lysine, per se.
Lysine is an amino acid used extensively in the animal feed industry, the major form of which is L-LysineHCl (L-Lysine monohydrochloride). For many years, a solid form of L-LysineHCl has been produced by a multistep process of fermentation, purification, crystallization and drying. After fermentation, the resulting broth may be rendered cell free by filtration or centrifugation. After the broth is cell free, the lysine may be recovered from the fermentation broth by an ion exchange step that produces a liquid which is substantially lysine free base. This solution may then be concentrated by evaporation.
Hydrochloric acid was usually added to the concentrated lysine free base to form L-LysineHCl. This concentrated L-LysineHCl solution was crystallized to produce a product in the form of L-LysineHCl dihydrate (L-LysineHCl:2H2O). This crystallized solid was thereafter dried to have less than one percent moisture.
This conventional dry product may have shortcomings. For example, it is dusty. During the handling of the product, the dust results in a loss of valuable material and sometimes causes an incomplete formulation. Also, human working conditions are made less healthful and more difficult as a result of the dust contributed by the L-LysineHCl. Sometimes the product develops lumps during storage which are difficult to break up at the time of end use. In addition, the extensive use of an ion exchange makes this process expensive.
Direct spray drying of an L-Lysine fermentation broth avoids the extensive purification steps associated with the L-Lysine hydrochloride process, in particular the use of an expensive ion-exchange. However, consistent L-Lysine concentration in the final dry product is difficult to achieve because the L-Lysine concentration in a fermentation broth can vary considerably. Also, the dry product may be dusty and difficult to use.
U.S. Pat. No. 5,431,933 describes a process for the production of an amino acid feed supplement which xe2x80x9cstill contains most of the solids content of the fermentation broth.xe2x80x9d The production of a fermentation broth at the industrial scale with 40 to 50 percent L-Lysine content is very difficult to achieve from an operational standpoint. Malfunctioning fermenters, contamination, power outages, and operator error are quite common and are likely to lead to fermentation material that is less than about 40 percent L-Lysine. This difficulty is compounded by the impurities associated with the media components, many of which are unrefined and vary in solids content and nutrient value from lot to lot. To avoid variance in media, fermentation is constrained to specific and expensive media. These considerations may lead to an increase in operational input which is necessary to make a 40 to 50 percent L-Lysine product, leading to high manufacturing costs which may be prohibitive.
A process in which a non-dusty granular animal feed product is formed is described in U.S. Pat. No. 5,622,710. First, the fermentation broth is spray dried to produce particles which may include biomass. In the second step, the particles are converted into pellets by means of costly high shear mixing equipment.
European Application Number 91460051.5 describes a method of making a granulated L-Lysine dust free, free-flowing, L-LysineHCl granular product from a liquid solution or slurry by a spray granulation process. In one embodiment of the invention, elements from a fermentation broth containing L-Lysine is ion exchanged to produce a purer L-Lysine solution. Hydrochloric acid is then added to the purer L-Lysine solution to make L-LysineHCl which is then sprayed onto an agitated drying bed of L-Lysine particulates. The particles of L-LysineHCl are then recovered once they reach a predetermined size.
International Publication Number WO/95/23129 describes the production of non-stoichiometric salt of L-Lysine in granular form. This publication teaches the production of non-stoichiometric salts of L-Lysine wherein the amount of L-Lysine content in the final product is adjustable. While the requirement for hydrochloric acid is reduced, other materials are called for such as calcium-hydroxide, sulfuric-acid or phosphoric acid. In addition, the fermentation broth containing the L-Lysine is extensively ion-exchanged.
U.S. Pat. No. 3,089,824 describes the use of a fluidized bed for the manufacture of compressed tablets for medical use. The process comprises (1) forming a suspension of particles in air, (2) enabling the particles to be built up with granulating material, and (3) coating the resulting granules with a lubricant. In one aspect of this invention, the granulating material is atomized and sprayed into the air-stream of a fluidized bed of inert particles such as sucrose. The inert particles act as nuclei for the granulation process. The resulting granules are coated with a lubricant.
The parent application (Ser. No. 08/991,145 filed on Dec. 16, 1997) now U.S. Pat. No. 5,990,350 describes an extremely useful process for making a substantially non-dusty granular L-Lysine product in which the concentration of L-Lysine in the final product is controlled by the addition of material containing L-Lysine, which is added prior to an agglomeration step (i.e. spray granulation step). There are occasions where a non-granular L-Lysine feed supplement with an adjustable amount of L-Lysine purity is desirable on economic grounds.
As useful as the copending and preceding parent applications are, their processes describe an ultrafiltration step to provide a substantially cell free L-Lysine broth and a cell rich L-Lysine broth in the form of a permeate and a retentate respectively. In the first application, the cell rich L-Lysine broth was abandoned as waste. The ultrafiltration step adds considerably to plant costs.
Care should be taken either to use or to properly dispose of the cell rich L-Lysine broth. The cell rich L-Lysine broth is frequently treated as a waste by-product and requires primary and secondary waste water treatments. If the cell rich L-Lysine broth is released as untreated sewage this may have a deleterious impact on the environment.
There are two major and several minor problems which may be encountered during the production of L-Lysine. First, a liquid L-Lysine product may experience degradation and solidification. The degradation is often caused by an effect upon microbial action brought about by changes in pH or by changes in osmotic pressure.
These problems may be alleviated by mixing a high purity, high pH free base lysine solution with the liquid streams of L-Lysine taken from a multistep production line. This mixture containing a free base lysine stabilizes both the pH and the osmotic pressure, which prevents lysine salts from crystallizing, thus insuring a retention of the lysine in a liquid form. As a result, microbial action is fairly well insulted from change.
Among the minor problems in lysine production is a need to provide a variety of products which can be easily tailored to fit an individual customer""s specification. For example, among other things, the customer may request liquids having a specific percentage of lysine. Also, some customers may prefer the lysine in a dry form while other customers prefer it in a liquid form. Hence, it is desirable to provide a production line which may be easily adjusted to meet specific specifications of individual customers. Another of these problems is that most of the above described processes lead to L-Lysine in a powder form, while many customers want to have their lysine in a liquid form.
Accordingly, an object of this invention is to provide a more flexible process to produce a L-Lysine product in which the concentration of L-Lysine in the final product is controllable. Another object is to provide a process which employs cell rich L-Lysine broth to produce a L-Lysine product in which the concentration of L-Lysine in the final product is controllable. Yet another object is to provide a non-granular L-Lysine feed supplement with an adjustable amount of L-Lysine wherein the spray granulation step is replaced with alternative methods of drying such as spray drying, drum drying, rotary drying, tray drying, and tunnel drying.
In keeping with an aspect of the invention, these and other problems are solved and objects are accomplished by selecting and mixing partially processed liquids taken from various points in the multistep manufacturing process for L-Lysine. If the correct amounts of such liquids are mixed in the correct proportions, almost any reasonably anticipated L-Lysine product may be produced. For example, such a product may have a portion of L-Lysine free base solution in the range of about 30%-50% wt. L-Lysine. The 30% end of this range is arbitrarily selected because if the lysine content is less than that, too much freight is being paid to ship water. The 50% end of this range is selected as a figure which is low enough to avoid crystallization under the worst case that is reasonable expected.